1. Field of the Invention
The present invention is directed to the field of electronic reproduction technology and is directed to a method and to an apparatus for picture-element-by-picture-element and picture-line-by-picture-line recording of printing forms, particularly for multi-color printing, wherein the recording signal required for the control of the recording element is called in from a signal source.
2. Description of the Prior Art
Before the printing form recording, individual originals for images and texts from which printed pages are to be compiled are first opto-electronically and trichromatically scanned in a color scanner in order to acquire color signals. In the case of four-color printing, a color correction computer corrects the color signals into color separation signals for the color separations "yellow", "magenta", "cyan", and "black". The color separation signals specify the required dosings of the inks for printing. The color separation signals of the individual originals are digitized into color separation data and are intermediately stored. Based on a lay-out plan, images and texts are then assembled in an electronic image processing system to form the individual printed pages and the color separation data of all printed pages of a printing order are first deposited in a data source for further employment in the sequence required for recording.
These work steps generally ensue long before the printing form recording, the color separation data being read out from the data source therein and being employed for controlling the recording element of a recording equipment.
In the case of printing form recording for offset printing, the recording equipment is a black/white recorder with which the rastered color separations of the printed pages are exposed on a film material or directly on printing plates. In printing form recording for rotogravure printing the recording means, by contrast, is an engraving system with which the rastered color separations of the printed pages are engraved on printing cylinders.
The problem to be solved shall be set forth with reference to the example of printing form recording for a merchandising catalog. A merchandising catalog comprises a plurality of printed pages and every printed page is in turn composed of pictures of merchandise, descriptions of merchandise, title and price particulars. It frequently occurs in practice that individual image or text originals are still outstanding in the production of the color separation data for the data source, so that the corresponding printed pages of the merchandising catalog cannot be assembled and the color separation data of these printed pages cannot be incorporated into the data set of the data source. It likewise occurs that printed pages of the merchandising catalog whose color separation data are present in the data set of the data source are up-dated by supplementary information, or that entire printed pages must be replaced by more current printed pages. A typical informational supplement, for example, is subsequent copying of current texts, titles, prices, etc. onto the background of a printed page.
Given such up-dating changes to and/or supplements of a printing order, it was previously necessary to repeat the electronic page montage with the modified or up-dated images and texts in order to transfer the new color separation data into the data set of the source and rework the overall data set on the basis of a sorting run. Since the original of the current images of texts are usually film originals, but wherein electronic page montage functions with color separation data, i.e. film-free, the current originals must also then be converted into color separation data by optical scanning and digitization before the electronic page montage. This procedure is time-consuming and hardly justifiable in view of the required up-to-dateness in the printing industry.